BirdAnalyst
Species · BBS 2025 Release · 1966–2024

Varied Thrush

TurdidaeForest birdsIxoreus naevius

Varied Thrush has surged: up 647% on the route-weighted index since 1970.

+647%Since 1970TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
304RoutesSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
56Years SurveyedYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

About the Varied Thrush

The Varied Thrush (Ixoreus naevius) is a North American member of the Thrushes (Turdidae). In this analysis it is grouped with the forest birds.

Size
6–11 in long (15–28 cm) — a medium songbird (typical for the family)
Habitat
Woodlands and forest edges, including wooded suburbs and parks.
Diet
Insects and spiders gleaned from foliage and bark, with seeds and berries in season.
Range
Recorded on 304 Breeding Bird Survey routes across 6 states, most concentrated in the Northern Pacific Rainforest.
Family
Turdidae · Forest birds

Notable Varied Thrush TrendsNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

long arc increasecomputed indexTrend sourceWhether the figure is our own computed route-weighted index or an official USGS modeled estimate. The current build labels every trend as computed.Full methodology →

Varied Thrush has surged in surveyed states: up 647% on the route-weighted index since 1970.

Varied Thrush Population Forecast

If the recent trend holds, Varied Thrush is projected to rise about 70% by 2029 — from 0.66 in 2024 to a central estimate of 1.1 (95% range 0.71–1.5). A 5-year backtest shows a typical error of ±61.3%, with 20% of held-out values landing inside the 95% band.

+70%Change by 2029TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
1.1Projected 2029 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.71–1.595% range95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
±61.3%Backtest errorBacktest errorTypical error when we hold out the most recent years, forecast them, and compare to what actually happened. Lower means a more trustworthy projection.Full methodology →
If the recent trend holds, Varied Thrush is projected to rise about 70% by 2029 — from 0.66 in 2024 to a central estimate of 1.1 (95% range 0.71–1.5). A 5-year backtest shows a typical error of ±61.3%, with 20% of held-out values landing inside the 95% band.19682029
Projection of the recent trend (dashed) with 80/95% bands — a projection, not a prediction. Habitat, climate, and land use are not modeled.
YearProjected indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →95% low95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →95% high95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
20251.10.641.5
20261.10.661.5
20271.10.681.5
20281.10.691.5
20291.10.711.5

Where the Varied Thrush Is Detected

BBS routes recording Varied Thrush, sized by most recent count.

Varied Thrush Population Trend by State

Varied Thrush population trend by state.
TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
Alaska+143%1973119
California-65%197022
Idaho-10%197224
Montana+12%197124
Oregon-62%197055
Washington-5%197060

Varied Thrush Population Trend by Region

Bird Conservation Regions are the ecological unit for trends.

Varied Thrush population trend by Bird Conservation Region.
TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →Baseline yearThe first year of the smoothed window the trend is measured from. An earlier baseline means a longer record stands behind the number.Full methodology →Survey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
BCR 2-4%198516
BCR 4-14%197667
Northern Pacific Rainforest+366%1970116
Great Basin-47%197030
Northern Rockies-16%197069
Coastal California+58%19963

Varied Thrush Conservation Status

Our route-weighted index shows it up about 647% since 1970.

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22. Trend is a route-weighted relative-abundance index, not an absolute population.